Why not double up on the ground and not have a spare?
I like your idea, what is that thing? Brand and part number?
DT
almost there..... sounding superb, I have a tiny bit of instability in the right channel, it ocasionally wants to oscillate so i will change the lead dressing and install cathode and anode stoppers, I'll also check its not the CCs.
D3a's dialed in at 17.2ma by ear (1.7v led bias).
B+
D3a's dialed in at 17.2ma by ear (1.7v led bias).
B+
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
no probs, the basic schematic is as follows
Tubed by ear, 3.3uf caps sound best, 17.2ma bias.
Its interesting to play with the impadance switch too, 5k load quite different to 10k with the d3a.
An externally hosted image should be here but it was not working when we last tested it.
Tubed by ear, 3.3uf caps sound best, 17.2ma bias.
Its interesting to play with the impadance switch too, 5k load quite different to 10k with the d3a.
Love the spud headphone amps, so cheap to build compared to commercial yet so much better. My job has gotten in the way of fishishing my Salas reg singlefeed OPT 5842 but I am getting closer.
cheers for a job well down.
cheers for a job well down.
I see, schematic is very straightforward... (and sorry for asking.. didn't remember that it was posted earlier in the thread 😉)
I second Regal in that spud headphone amps are great... I just converted my C3G-based amp from post #34 to custom SE output transformers (from Reinhoefer in Germany), and they went another league up. Also are absolutely dead quiet.
Now I just have to case it up as nicely as Adamus did
I second Regal in that spud headphone amps are great... I just converted my C3G-based amp from post #34 to custom SE output transformers (from Reinhoefer in Germany), and they went another league up. Also are absolutely dead quiet.
Now I just have to case it up as nicely as Adamus did
Nice use of source and sink. I've used the same in my designs.
Cascode DN2540 as source and led as bias. Nice synergy between the 2.
Cascode DN2540 as source and led as bias. Nice synergy between the 2.
I sorted the oscillation in the right channel, it was the long(ish) lead length of the cathode led. Moving the led to the pin cured it. I wonder how many people build amps like this with slight oscillation and never notice it, it puts a real metallic sheen on the sound, makes it slightly harsh.
I have put some listening time into this amp... its in a different league to my previous attempts. I am SUPER impressed with Jacks transformers.
the D3a's are very good for the money, I run them at about 17ma @1.7v bias. Pushing towards 20 brightens the sound a tad, not to my taste.
I'll soon get the opportunity to test some edcor parafeed Tx's, at a 1/5 of the cost it will be interesting to see how near the get.
I have put some listening time into this amp... its in a different league to my previous attempts. I am SUPER impressed with Jacks transformers.
the D3a's are very good for the money, I run them at about 17ma @1.7v bias. Pushing towards 20 brightens the sound a tad, not to my taste.
I'll soon get the opportunity to test some edcor parafeed Tx's, at a 1/5 of the cost it will be interesting to see how near the get.
I am just about to throw together a parafeed spud headphone amp; If the power transformers are toroidal does anyone think I need 2 boxes? Thanks.
At the very least lay it out and try it before commiting to a chassis, some headphones can be very sensitive, its hard to predict.
Thanks regal, do you mean sensitive in the same respect that speakers are sensitive or that the transducers themselves easily pick up EM fields?
agree with regal, test it before cutting holes. Regal means sensitive in the same respect to speakers, any noise in the amp is easier to hear in sensitive cans that insensitive as by definition, senistivity is the volume produced per watt.
I am using a single box at the moment with a parafeed setup and its fine even with grados. That is with a rcore transformer which emit less em than EI. Toroids theoretically should be even better.
I needed 10 inches as a minimum gap for silent operation, you may need more or less depending on the transformers used.
I am using a single box at the moment with a parafeed setup and its fine even with grados. That is with a rcore transformer which emit less em than EI. Toroids theoretically should be even better.
I needed 10 inches as a minimum gap for silent operation, you may need more or less depending on the transformers used.
Hello,
Been there done that.
To my ears and brain it is really disruptive to hear any hum or buzz from the headphones. My solution was to put the transformer(s) in a separate enclosure with C L C filter for the B+ and C R C for H+. Then install regulators in the amplifier enclosure. Over kill; I do not think so, silent like the grave yard.
DT
All Just for fun!
Been there done that.
To my ears and brain it is really disruptive to hear any hum or buzz from the headphones. My solution was to put the transformer(s) in a separate enclosure with C L C filter for the B+ and C R C for H+. Then install regulators in the amplifier enclosure. Over kill; I do not think so, silent like the grave yard.
DT
All Just for fun!
Thanks guys;One of the components that I am concerned about EM pickup is the input pot. I would like to use a wirewound one-I have some,which are very nice. Anyone tried this before?
Hello,
The pot is most likely no different than the point to point wiring or PCB whatever you are using. Ground the case of the pot if it is metal, I would say.
DT
All Just for fun!
Thank you, DT, your answer is very logical and I couldn't say anything in disagreement. My question was prompted by the fact that I did once experience buzz at maximum headphone volume with a very high impedance(1 Meg) shunt attenuator I built.
Hello,
Hum, buzz, switching diode noise and their harmonics are ubiquitous. I have a hunch that your attenuator may be the innocent bystander standing too close to the crime scene. It is suspect due to proximity. The input selector switch and wiring connections are also suspects. I am a believer in also switching the ground so that only one source and its related ground are attached at once. You do not want a ground loop coming in and attaching to the signal ground. Only one source grounded at a time.
The headphones sit on your head just millimeters from your ear, the buzz can not hide.
DT
All Just for fun!
Yes,I had come to the same conclusion about proximity; there are 4 choke input PSU's in aluminium boxes reasonably nearby.Also,being in London,there is interference everywhere. The trouble is, I REALLY hate working with steel-although if my father's machine shop were not 400 miles away it would be easy!. Actually, because 98% of my listening is LP's or 78's I do not switch sources, I merely change over connections. Also,my system is differential all the way through so I am perhaps a little less susceptible to ground problems.
This headphone amp will be a present for my sister who suffers badly from insomnia-I am hoping it might help a little and am particularly concerned there will be no dratted hum!
This headphone amp will be a present for my sister who suffers badly from insomnia-I am hoping it might help a little and am particularly concerned there will be no dratted hum!
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